Semiconductor memory devices store data and/or program code for many types of electronic systems. These electronics systems include personal computer systems, cellular phones, music players (e.g., MP3 players), image processing circuits, and the like. In order for these memory devices to be useful, it is important that they accurately store data.
Radiation is one factor that may contribute to data errors in these memory devices. When a single charged particle, for example an alpha particle, travels through a semiconductor, it leaves an ionized trail behind it. The ionization may affect the device in one of several ways. For example, the ionization can cause a temporary glitch, can cause a bit in a memory cell or register to “flip”, or can even cause destructive latch-up and burnout.
A “bit flip” occurs when a single radiation event interacts with the device and causes a memory cell or register cell to change state. Such a flip or upset in bit state is referred as single-event upset (SEU), These SEUs do not necessarily cause lasting damage to the device, but may cause lasting problems to a system that cannot recover from such an error. In some devices, a single radiation event can also cause a multiple-bit upset (MBU) that flips data in several adjacent memory cells.
In order to ensure proper operation of memory devices and other electrical systems, manufacturers of integrated circuits use various methods of radiation hardening to protect against radiation events. The present invention relates to methods and systems for mitigating the effects of radiation on integrated circuits.